The most popular types of low profile strain relief cord grips on the market today commonly consist of several pieces that are molded of plastic. A locking nut portion is typically tightened once the cable is inserted within the separate pieces of the connector and the tightening action causes several fingers to close upon the inserted cable and grip it in place.
U.S. Pat. No. 3,991,446 describes a one-piece knock-out plug that can be applied to a wide range of knock-outs in a junction box, but makes no mention of a wide range of cable sizes. U.S. Pat. No. 3,991,446 is very limited on the size of cable that may be used in conjunction with it. There is no mention of the tightness of grip on the cable or the liquid-tightness of the grip. The bushing of U.S. Pat. No. 3,516,111 is substantially different from the disclosure of this invention, with a thermoplastic connector containing fingers that exert force on an inserted cable. As mentioned in the patent, the bushing will "tend to hold such element against counter movement from the direction of insertion without precluding counter movement". The bushing of U.S. Pat. No. 3,516,111 therefore does not provide strain relief as does the cord grip of this invention.
U.S. Pat. No. 3,788,655 relates to a one-piece grommet that can be used for sealing a cylindrical object in an aperture of a panel. This grommet is strictly limited in the range of size of cylindrical object that may be inserted within it. Also, no mention is made of the strain relief capabilities of the grommet.
The anti-rattle bushing mentioned in U.S. Pat. No. 3,768,115 is intended to prevent metal to metal contact between a lever arm and an actuator rod and as such does not relate closely to strain relief cord grips.
U.S. Pat. No. 3,506,999 mentions two symmetrical plastic pieces that form a grommet that is intended to form a seal around a control cable. A given size grommet is applicable to one size cable only and no mention is made of strain relief capabilities.
A grommet that is particularly adopted for deployment around the push-pull knob of an automobile lock is disclosed in U.S. Pat. No. 3,351,974. It is substantially different than a strain relief cord grip as the grommet is not designed to tighten upon the inserted door lock.
A self-locking insulating sleeve, designed to be pushed into the aperture of a panel, is mentioned in U.S. Pat. No. 3,197,556. No mention is made of the sleeve's capability to accept a wide range of cable sizes. The sleeve has limited strain relief capabilities as the invention mentions the ability of an operator to "exert a force that is sufficient to cause withdrawal" of the sleeve from the opening in the wall structure.
This disclosure thus improves upon all of the aforementioned prior art by providing a cord grip that:
1) is of a simple construction and can be easily and cheaply mass produced, PA1 2) is of a low profile to allow ganging of cables in close proximity to one another, PA1 3) provides a firm yet non-abrasive grip or bite on the cable, PA1 4) forms a liquid-tight seal around the cable, and PA1 5) accepts a wide range of cable sizes.
The novel features of this invention are described in detail in the following sections and in particular in the appended claims.